Field of the Invention
The invention relates to an electrical power storage system. More specifically, the invention relates to an energy storage system with a “green” environmentally friendly maintenance discharge function wherein the energy discharged during a maintenance discharge cycle is provided to the host power rail and consumed by the host system load instead of being dissipated as heat.
Description of Related Art
Energy storage systems may utilize energy storage cells, for example banks of batteries, as the energy storage media. Where engagement of the energy storage system is a rare event, for example where the energy storage system is part of an uninterruptible power supply (UPS), regular maintenance discharge/charge cycles of the energy storage cells may be required to maintain optimal charge level and/or verify continued energy storage cell viability.
Maintenance discharge/charge cycles are typically performed by a maintenance discharge control 25 circuit of the battery management system, for example as shown in FIG. 1. The thermal discharge control 25 circuit routes the energy stored in the energy storage cells 1 to a load resistor 3 which dissipates the stored energy as heat. This heat generation may in turn consume additional energy if the heat generated by the load resistor 3 must be further removed from the system area by the surrounding air conditioning apparatus. Once discharged to the desired energy level, the energy storage cells 1 are then re-charged by conventional charge control 10 circuitry.
Competition within the electrical power storage industry has focused attention upon increasing reliability, system uptime, energy cell longevity and overall system energy and cost efficiencies.
Therefore, it is an object of the invention to provide an energy storage system that overcomes deficiencies in such prior art.